Experimental Study Of Early Strong Grouting And Mechanism Analysis For Prestress Anchor

Presently, Common Silicate cement liquid is more generally adopt to prestress anchor engineering in our country, whose condensing time is longer, and earlier peiod strength of the anchor solid is lower. As sample conservation time after grouting anchor hole is more than seven days,the press strength of grouting solid is can attained 15-25 MPa, locking work of anchor being also carry on at this time, which should bring about a problem out of shape to soil body of needing the side ascent protect as executed stress to anchor in advance, meantime it lead long construction period for anchor engineering. From this, to carry on changing character research and to highen the earlier peiod strength should be very necessary for Common Silicate cement liquid, and the studing content should take on great innovation,and study production padded vacancy on prestress anchor technology in our country.Because the geology condition of rock and soil, the technique condition of construction is more complicated and changed , and anchor solid (including anchor pole and grouting body) is subjected to the restrict of numerous factors in mechanics behavior within geotechnical body , it should take more difficulty to anlyze of theories and actual measure , must result in lacking of universality and accuracy for some results. As a result of that research of mechanism in anchor engineering still was lagged to its applied realm,it has restricted the futher development of application study for anchor technique. Thus, it all are very necessary and innovatory to different type of prestressed anchor pole such as wholly grouted anchor rod, type of internal anchor solid, type of pulling force concentrated and pulling force decentralized, pressure force concentrated and pressure force decentralized etc, establishing the calculation model of higher coincidence to deliver mechanics of anchor, and describing the stress distribution rules of anchor with accuracy, and calculating the its basic solution.In this subject, study on above-mentioned problem is in progress, the contents include:(1)choices of cement,s additive and study of its function mechanism;(2)experimental study and practice application effect of early strong grouting material;(3)function machanism of splitting grouting and development of new stopping grout for anchor pole;(4)activity effect and stimulating approach of fly ash;(5)property influence of silica ash to early strong cement grouting ;(6)bearing capability influence and increasing strength on fiber to anchor pole;(7)research of stress distribution rules on anchoring segment for prestressed anchor pole.Through experiment research, production test and foundation of computing model, breakthrough development have been obtained on the task study, have get innovation production and innovatory conclution as follows:(1)According to requirement of grouting and locking work for prestress anchor pole,through experimental study of grouting modification, the Common Silicate cement grouting direction with increasing its early intensity have been obtained. For the grouting, water cement ratio is in order (W/C=0.45~0.60),and pumping period (≥15min) of the cement slurry is suitable, and original coagulating time is 4~6h,and terminal condensing time is in 12h,the press strength of Common Silicate cement grouting liquid could increase 50 to 120 percent than no-modificated cement grouting in two or three days condensing time, that it is 15~25MPa, and upper intensity can steadily increasing,which would greatly enhance the construction speed of anchor engineering,and control displacement of shoring slope in time.And engineering practice shows that application effect of cement grouting which have beed modified is very well, it should have popularizing application value.(2)For special anchoring engineering,Aluminum cement grout (i.e. high Aluminum cement) can be choose according to the demand of engineering. The pumping period can,t be influenced,as the right amout of fly ash is mixed into Aluminum cement grou(tadding to proportion 25~50%),at present water solid ratio being equal to 0.45~0.50, press intensity of 24h condensing ime can reaching 15MPa above. It can lower economic costs to some extent and make for environmental protection,that fly ash mixed into Aluminum cement grout. At the same time ,study on Activity effect and stimulating approach of fly ash have been made more thorough .(3)The affect mechanism of splitting crack grout have been analysed for the soil layer anchor pole,deducing of calculation parameter was completed for splitting crack grout. In this foundation, carried on press calculation of splitting crack grout for rock layer anchor pole. Besides, implement on stopping grout by annular press for anchor was devised, which was impowered practical new patent by Bureau of Intellectual Property Rights Chinese.(4)To mix in suitable quantity of silica ash to Common Silicate cement grout, i.e. 3~10% of cement quantity,it can markedly increase press intensity of grouting concretion solid,because silica ash have action following aspects :①the effect of volcano ash of high activity;②raising interface resultant force between cement stone and aggregate material;③improving bore structure of cement stone or concrete.In order to increase forepart press intensity of concreting and induration on cement grout, silica ash should be mixed into it, but the adding quantity of silica ash should being controlled within 10 percent, with possibly lowering constringency rate on cement grout sclerosesing behind.(5)For the anchor solid engineering,to mix in a little quantity of fiber production such as glassfiber,polypropylene fiber to cement grout or cement sand gtout,adding fiber quantity should being controlled within 0.05%～0.15% of cement quantity, it can obviously increase the press intensity and the impact toughness and the split ability of concreting body on cement sand grout, improve shearing intensity of felting between cement sand grouting solid and anchor hole wainscot rock body, generally it can raise above 20% comparing with common cement sand grout. In the meantime, it can also improve bearing circumstance, strengthen the extreme loading of anchoring solid, reinforce safeguard to anchor, and reduce loss of prestress for anchor.Because of active effect of fiber sand grout, the strength storage of anchoring pole can gain heighten.(6)For wholly grouted type anchor rod, friction resistance round anchoring segment cement sand grout and its circumference rock–soil body accord with index distributing,its function is: distributing formula on shaft force of anchor pole is: Emphasized to analyze the problem that modality of anchor pole bore wall influence to anchor loading.(7)For internal pulling type anchor pole,through establish of model and elasticity solution on anchoring mechanics,deduced distributing function of shearing stress round anchor solid body,its function is:through Kelvin displacement solution,get distributing function of shearing stress along anchoring solid body,its function is:(8)For pulling force decentralized type anchor pole,distributing function of shearing stress along anchoring segment is equal to its piling up each,i.e.:(9)For solid pressure force concentrated type anchor pole, distributing function of shearing stress and shaft force for anchoring pole or cable is:(10)For pressure force decentralized type anchor pole, pile up distributing of shearing stress and shaft force along anchoring segment each:For pressure force decentralized type anchor pole, strength of anchoring geologic strata can be utilized fully, to come true higher anchoring power. Through thorough discuss ,put forward a calculation method of the extreme loading which has characteristic of amelioration and innovation on anchor of pressure force decentralized type.Length unit of each anchor segment take 4~6 meter as proper for pressure force decentralized type anchor pole.